Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!

Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.

COBB Tuning is proud to announce the immediate availability of our proprietary Speed Density (SD) tuning solution for all currently-supported 2.5L USDM turbocharged Subaru vehicles! This capability is available as a free update to our AccessTUNER Pro software and AccessPORT firmware. Our implementation of Speed Density adds our proprietary tuning logic to the factory ECU, enabling it to calculate load, ignition and fueling requirements using the engine’s manifold absolute pressure (MAP) sensor, instead of the factory mass airflow (MAF) sensor. COBB Tuning’s exclusive Realtime tuning capabilities and Hybrid Logic (active switching between MAP and MAF based logic) make this a uniquely powerful and flexible engine management solution. Read on for more details about the work COBB Tuning is doing to make sure the AccessPORT is the most comprehensive OEM ECU tuning solution available for Subaru performance enthusiasts.

Why Speed Density
The most basic function of an engine control unit (ECU) is to measure airflow and its translation to engine load. Precise and consistent load calculations along with feedback from other critical sensors allow the ECU to accurately control ignition timing, variable camshafts, and fuel delivery. The most common way to measure load in modern vehicles is with a MAF sensor. Vehicles with stock engines and mild upgrades can utilize the MAF sensor with excellent overall results. However, in big-build and motorsports applications where power levels are extremely high and intake airflow configurations are less standardized, the use of a MAF sensor can be limiting.

Speed Density tuning using the Subaru factory ECU is a major break-through for high-power Subaru builds. High-power builds using the OEM MAF sensor require very large MAF intake housings to keep the MAF sensor within its usable range, which introduces reduced resolution and unpredictable turbulence that can affect tunability and drivability. Eliminating the need for a very large, high-quality MAF intake housing using Speed Density tuning logic allows for more flexibility when designing a turbo kit and the associated piping and plumbing. Speed Density tuning gives precise control over fueling, timing and other critical tuning components necessary to properly calibrate the vehicle at the very high power levels that today's big Subaru builds are capable of producing.

Hybrid Logic - Ultimate Flexibility
The Speed Density update for AccessTUNER Pro software offers multiple ECU control modes to give the professional tuner and AccessPORT user a wider choice of engine modifications and tuning options. The software can program the ECU to run in the traditional pure MAF mode, a pure “Speed Density” mode, or a Hybrid Mode which uses both MAF and “Speed Density” with dynamic logic switching between the two.

Ease of Conversion
In order to make the transition to Speed Density as painless as possible, COBB Tuning has streamlined the process within the AccessTUNER software. Simply open an existing MAF-based calibration using the new Speed Density enabled software and resave the map. All of the tables from the MAF-based calibration will be loaded into the Speed Density based calibration. You are now ready to start tuning the Volumetric Efficiency (VE) table without the need of starting a new calibration from scratch!

Speed Density Availability
This initial release of Speed Density is available for professional tuning shops using AccessTUNER Pro software for turbocharged Subaru USDM vehicles. Speed Density for AccessTUNER Race is currently in development and will be made available to self-tuners once development and testing is completed. “Off-The-Shelf” maps will not be made available for Speed Density as custom calibration specific to each vehicle is required.

Currently, the following USDM 2.5L turbocharged Subaru vehicles are supported:

It took us quite a bit longer than anticipated to develop Speed Density for all USDM 2.5L turbocharged Subaru vehicles, but now that it is complete, we are very excited about this release. We have combined our proprietary Speed Density logic with the flexibility of Hybrid Mode dynamic logic switching, the convenience of the AccessPORT’s Realtime tuning capabilities and the sophistication inherent in the factory ECU, bringing a powerful and unique solution to meet a large and long-standing demand in the Subaru enthusiast community. We would like to thank you for your patience and want to hear your feedback regarding Speed Density on your Subaru!

To learn more about our implementation of Speed Density, please download the Subaru 2.5L Speed Density Tuning Guide. If you are interested in becoming a new Subaru ProTUNER capable of tuning customer vehicles with Speed Density, please give us a call at 866-922-3059.

POTENTIAL RISKS FOR SD WITH A HEAT SOAKED IAT SENSOR
Any SD calculation, including COBB SD, requires an input for cylinder charge temperature, which is critical to the
determination of accurate airflow via SD. The estimation of cylinder change temperature is accomplished for COBB SD
via the IAT sensor input. Generally, when the IAT sensor is in the recommended location (post-IC), the vehicle is
moving and the driver is on the throttle, the IAT input can be a fairly reliable representation of actual cylinder charge
temp. However, when the vehicle is sitting still (or at low speeds) and the driver is off the throttle (or low throttle), or
the vehicle has been sitting with the engine off and a hot engine bay for a period of time, there is the potential for the
IAT sensor to become heat soaked. That is, the sensor now reads higher than the actual intake air temp. When SD is
active, this would cause the calculated SD airflow (as well as load) to be lower than it should be, causing the car to run
lean (and with generally more timing advance). This effect may subside after the vehicle gets moving and throttle (as
well as MAP) increases, but it will generally not be an instantaneous improvement. As such, it is critical that the
owner/driver of the car understands the specific scenarios in which a heat soaked IAT sensor can potentially occur and
to avoid putting the car under high load when these scenarios are present (and for a period shortly after). This is
another reason why a wideband o2 sensor and gauge should be installed in the car and that the driver instructed on
how to determine when fueling is incorrect.

• The owner of the car also needs to understand that practically any engine mod that impacts airflow in any way
may require a re-tune or tweaking of the VE table for cars running SD. This is important as even seemingly
minor mods that a MAF sensor-based tune would have no problem accounting for, might cause a significant
enough change in VE that there could be fueling and load issues for SD.

Cobb SD is badda$$! Played around with it on my own car today and I have perfect idle/cruise/mid load drivability and fueling with only about 30-45 mins of tuning the VE map and a couple comp tables. Have to find some time between customer tunes to get my car on the dyno and verify that the higher load sections but that should be even quicker.

A typical car that would necessitate an SD tune
would likely max out the factory MAP sensor and require an aftermarket MAP sensor to be installed

It basically says you need an aftermarket MAP Sensor. Can you all give a recommendation on a MAP sensor?

Quote:

The MAF sensor assembly must be installed and properly calibrated if the MAF mode, hybrid
mode, or estimated VE monitor is to be used. It must also be installed if the factory IAT sensor (which is part of
the MAF sensor assembly) is to be used for SD (rather than an aftermarket IAT sensor).

From reading that it sounds like the maf can be removed and an IAT sensor be used instead if going the pure SD route, can you all give a recommendation on an IAT sensor?

It basically says you need an aftermarket MAP Sensor. Can you all give a recommendation on a MAP sensor?

From reading that it sounds like the maf can be removed and an IAT sensor be used instead if going the pure SD route, can you all give a recommendation on an IAT sensor?

Kmook - You read correctly. On page 24 of the SD Guide you can find many recommendations and calibration settings for the IAT and MAP sensors. The calibration listed for IAT is based on the GM/AEM IAT sensor (3/8" Bung Style).

POTENTIAL RISKS FOR SD WITH A HEAT SOAKED IAT SENSOR
Any SD calculation, including COBB SD, requires an input for cylinder charge temperature, which is critical to the
determination of accurate airflow via SD. The estimation of cylinder change temperature is accomplished for COBB SD
via the IAT sensor input. Generally, when the IAT sensor is in the recommended location (post-IC), the vehicle is
moving and the driver is on the throttle, the IAT input can be a fairly reliable representation of actual cylinder charge
temp. However, when the vehicle is sitting still (or at low speeds) and the driver is off the throttle (or low throttle), or
the vehicle has been sitting with the engine off and a hot engine bay for a period of time, there is the potential for the
IAT sensor to become heat soaked. That is, the sensor now reads higher than the actual intake air temp. When SD is
active, this would cause the calculated SD airflow (as well as load) to be lower than it should be, causing the car to run
lean (and with generally more timing advance). This effect may subside after the vehicle gets moving and throttle (as
well as MAP) increases, but it will generally not be an instantaneous improvement. As such, it is critical that the
owner/driver of the car understands the specific scenarios in which a heat soaked IAT sensor can potentially occur and
to avoid putting the car under high load when these scenarios are present (and for a period shortly after). This is
another reason why a wideband o2 sensor and gauge should be installed in the car and that the driver instructed on
how to determine when fueling is incorrect.

• The owner of the car also needs to understand that practically any engine mod that impacts airflow in any way
may require a re-tune or tweaking of the VE table for cars running SD. This is important as even seemingly
minor mods that a MAF sensor-based tune would have no problem accounting for, might cause a significant
enough change in VE that there could be fueling and load issues for SD.

You are correct - that would be the two things to consider when going with any SD solution. We have found that placing the IAT sensor post-intercooler (in the case of front-mount) is the most accurate means of estimating charge temp and, generally speaking, the best location to minimize IAT heat soak. The factory IAT sensor is housed in the MAF-sensor assembly, so if the MAF sensor is removed, you'll need to go with an aftermarket sensor.

All cars using SD should be running a wideband o2 sensor with in-car gauge. That is really a no-brainer and even cars still running MAF at power levels that would benefit from SD should have this set-up anyway.

Can you use the stock map sensor for pure SD tuning? as long as your running under 23psi of course?

Yes, you can use the stock MAP sensor, but you have to make sure that you are not going to exceed the limits of your factory sensor under any conditions. For example, you may find yourself hitting a higher MAP under colder conditions. Also keep in mind that 23 psig is just a guideline as to the limit of the factory sensor - some factory sensors may not necessarily read that high (or become inaccurate near their limit). Just as if you maxed out the factory MAF sensor, maxing out the MAP sensor will cause you to go lean in SD mode as actual MAP is greater than reported MAP.

I'm planning on using the stock map sensor but i plan on never going past 20psi on a vf39

You should be fine then - just make sure you set your boost limit fuel cut appropriately. Generally, though, if you are nearing the limit of the sensor, you might as well upgrade as some point - it is easy to do and we've provided the calibration data in the SD guide for a lot of the common aftermarket MAP sensors.